A partially wetting droplet on a substrate behind an obstacle in a sufficiently strong wind is found experimentally to depin and move downstream, or depin and move upstream, or split into two. A simple 2D theory gives a qualitative prediction of this behavior.

An experimental investigation of oscillations of Leidenfrost drops finds that the oscillations are driven by capillary waves beneath the drop.

Experiments with a largely inelastic shear-thinning fluid in a cylindrical pipe find the asymmetric flow previously associated with laminar-turbulent transition appears to have the characteristics of a nonhysteretic, supercritical instability of the laminar base state.

For Reynolds numbers Re${}_{\theta }<10,000$, the dissipation parameter $C_{ϵ}$ is found to vary in the streamwise direction in constant-pressure turbulent boundary layers and is inversely proportional to the turbulent Reynolds number Re${}_{\lambda }$.

Two-dimensional turbulence gives rise to surprising, symmetry-breaking, large-scale patterns. A numerical study reveals a mix of vortices and jets, sensitive to friction and box aspect ratio, instead of a dichotomy between the two. The resulting mean flow changes with the averaging time chosen.

Adding large non-Brownian particles to a cornstarch suspension moves the discontinuous shear-thickening transition to lower critical shear rates, allowing control of shear-thickening properties by varying large-particle concentration, while the stress at the transition is little changed.

An experimental investigation shows, and elaborates the conditions for, jetting flow of a shear banding solution through rectangular channels. Viscoelastic modeling replicates the observed flow transitions and elucidates the role of local stresses.

A series of cooled parallel vanes placed in a channel with heated sidewalls leads to gas flow along the channel when the reflection properties on opposite sides of the vanes differ.

An experimental investigation into the effect of cavitation, created from seeded microbubbles, on the dispersion of sprays is presented. The dispersion, determined through laser-induced phosphorescence, shows no significant difference between cavitating and noncavitating conditions.

Numerical simulations show that dissipation local to the contact line of an impacting droplet limits its maximum spreading diameter, which scales with a function of the droplet viscosity, the impact Reynolds number, and the contact line friction parameter.

The coupling and interplay of electrokinetic and Rayleigh-Bénard instabilities are experimentally investigated in the flow towards an ion selective interface. The flow, concentration profiles, and electrical response are measured and modeled based on Fick’s second law.

The helicity segregation characteristic of a monochromatic inertial wave is tested for a wave packet. The effect of several forces, such as those due to buoyancy and magnetic field, on this characteristic is also investigated.

The behavior of freely falling noncanonical particles is an important but scarcely investigated topic. Adding an elliptic protrusion behind a sphere leads to turn and drift of the body. The optimal shape of the protrusion yielding the largest drift is obtained.

The onset and characteristics of shear and thermal instabilities are considerably modified when incorporating electrically conducting fluids with an imposed transverse magnetic field. Short- and long-wavelength mixed instabilities are identified by a linear stability analysis of flows.

Instability of two-fluid co-flow jets is studied by high-fidelity numerical simulations. Interplay between viscosity ratio and surface tension creates three radically different instability regimes. A new instability mechanism due to surface tension is found in the jets and in two-fluid Couette flow.

Electrostatic suppression of Leidenfrost state is studied experimentally and theoretically. Linear stability theory successfully predicts threshold voltages required for different drop volumes and surface temperatures.

Ocean waves are attenuated when propagating in a marginal ice zone. A direct phase-resolved numerical model of nonlinear ocean waves in fragmented sea ice is proposed. Two-dimensional simulations quantify solitary wave scattering and attenuation through an irregular array of ice floes.

The effects of a no-slip wall on flagellar propulsion are investigated by experiments with macroscopic-scale model flagella and simulations based on algorithms from computer graphics. A nearby wall shifts the threshold for buckling of the flexible flagellum and increases the propulsive force.

An autophoretic torus can act as a pump or a swimmer. A series solution is derived, showing that these tori have nontrivial optimal behavior and can move faster than an equivalent spherical Janus particle.

The collapse of the superhydrophobic state on a nanopillared surface is investigated via rare-event molecular dynamics simulations, which show that the collapse mechanism is asymmetric and involves several pillars. Nanoscale effects are assessed by comparison with macroscopic continuum models.

Small bubbles occurring in water make turbulence in their wake. A model for such turbulence and a computational procedure for turbulence modeling in multiphase flow are proposed.

Particle-image velocimetry of a laminar immersed round jet and refractive index-matching of a granular medium are used together for accurate determination of the critical flow conditions enabling grain erosion, which is consistently described by a dimensionless inertial Shields number.

Bubbles that contain either vapor or an incondensible gas have been well studied. A model of a mixture of the two is presented and several resulting processes are examined, including temporary superheating, a burst of sound applied to such a bubble, and continuous growth in the presence of heating and incondensible gas.

Particle-induced turbulence modulation is discussed by physically regularizing the interphase momentum coupling. Contrary to standard approaches, small-scale statistics converge and highlight the role of the particles in modifying the energy cascade. A new spectral law is verified by direct numerical simulation data.

Dimensional analysis and numerical simulations show that the onset of sediment transport by a flowing fluid may be best described as the point when mobile grains can no longer stop, as opposed to when static grains start to move in response to fluid forces.

Large-eddy simulations of a fully developed channel flow are performed with friction Reynolds numbers of 550, 2000, and 5200 by using the recently developed explicit algebraic subgrid scale model. The model relaxes the required number of grid points by at least an order of magnitude for the same accuracy.

In experiments and computations for Newtonian fluids, low-drag events are identified in which the turbulence moves locally towards a lower-branch exact coherent state whose mean velocity profile is similar to the maximum drag reduction profile for polymer solutions.

We show that the discrepancies in Reynolds-averaged Navier-Stokes (RANS) modeled Reynolds stresses can be explained by mean flow features. A physics-informed machine learning framework is proposed to improve the predictive capabilities of RANS models by leveraging existing direct numerical simulations databases.

The dynamics of a bimodal 3D turbulent wake downstream of a square-back bluff body are investigated. The low-frequency large-scale dynamics of the wall-pressure barycenter trajectory exhibit the same characteristics as a weak strange chaotic system, with two well-defined attractors.

A Lie group symmetry analysis is applied to the sink flow turbulent boundary layers, where a similarity transformation is obtained mapping mean velocity profiles under different blowing and suction conditions into a universal profile.

A study of different families of chaotic or coherent instantonlike solutions in a class of inviscid models of the turbulent cascade finds nontrivial correlations between the anomalous scaling of the stationary viscous ensemble and the helicity contents of the instantons.

Contrary to previous explanations for the ubiquitous occurrence of the roll-streak structure in wall-bounded shear flows as arising only from coherent perturbations, new analysis shows that the roll/streak structure can also arise from destabilization of this structure by free-stream turbulence.

Application of equilibrium statistical mechanics to 2D fluids sheds light on both microscale turbulent fluctuations and macroscale features, such as Jupiter’s Great Red Spot. An analysis of the intricate interplay between eddy motions and surface wave fluctuations in the shallow water equations is presented.

Effects of buoyancy on fluid flow are studied through its action on countersigned light-cored vortex dipoles. Buoyant vortices can be modeled as spinning bodies experiencing a lift force. Theory and simulations show that buoyant vortex dipoles can annihilate, leading to large increases of enstrophy and kinetic energy.

A model equation for the 1D pilot-wave dynamics over a varying bottom is applied to tunnelling between two cavities.